The Galilean satellites were assigned their Greek mythological names by Simon Marius (commemorated on the Moon by a crater 27 miles across), a contemporary of Galileo and a disputant with him for the priority of their discovery. Marius and Johannes Kepler felt that it would be extremely unwise to name celestial objects after real people and particularly after political personages. Marius wrote: “I want the thing done without superstition and with the sanction of theologians. Jupiter especially is charged by the poets with illicit loves. Especially well-known among these are three virgins, whose love Jupiter secretly coveted and obtained, namely: Io… Callisto… and Europa… Yet even more ardently did he love the beautiful boy Ganymede… and so I believe that I have not done badly in naming the first Io, the second Europa, the third, on account of the splendor of its light, Ganymede, and lastly the fourth Callisto.”
However, in 1892 E. E. Barnard discovered a fifth moon of Jupiter with an orbit interior to Io’s. Barnard resolutely insisted that this satellite should be called Jupiter 5 and by no other name. Since then, Barnard’s position has been maintained, and of the fourteen Jovian moons now known, only the Galilean satellites had, until recently, names officially sanctioned by the IAU. However unreasonable it may be, people show a strong preference for names over numbers. (This is clearly illustrated in the resistance of college students to being considered “only a number” by the college bursar; by the outrage of many citizens at being known to the government only by their social security number; and by the systematic attempts in jails and prison camps to demoralize and degrade the inmates by assigning them a numeral as their only identity.) Soon after Barnard’s discovery, Camille Flammarion suggested the name Amalthea for Jupiter 5 (Amalthea was in Greek legend the goat that suckled the infant Zeus). While being suckled by a goat is not precisely an act of illicit love, it must have seemed, to the Gallic astronomer, adequately close.
The IAU committee on Jovian nomenclature, chaired by Tobias Owen of the State University of New York at Stony Brook, has proposed a set of names for Jupiter 6 through 13. Two principles guided their selection: the name chosen should be that of “an illicit love” of Jupiter, but one so obscure as to have been missed by those indefatigable cullers of the classics who name asteroids, and must end with an a or an e depending on whether the moon goes around Jupiter clockwise or counterclockwise. But in the opinion of at least some classical scholars, these names are obscure to the point of bewilderment, and the result leaves many of the most prominent Jovian paramours unrepresented in the Jupiter system. The result is particularly poignant in that Hera (Juno), the wife so often scorned by Zeus (Jupiter), is not represented at all. Evidently, she was inadequately illicit. An alternative list of names, which includes most of the prominent paramours as well as Hera, is also shown in the table below. Were these names employed, it is true they would duplicate asteroid names. This is in any case already a fact for the four Galilean satellites, where the amount of confusion thus engendered has been negligible. On the other hand, there are those who support Barnard’s position that numbers are sufficient; prominent among these is Charles Kowal [10] of the California Institute of Technology, the discoverer of Jupiter 13 and Jupiter 14. There seems to be merit in all three positions and it will be interesting to see how the debate turns out. At least we do not yet have to judge the merits of contending suggestions for naming features on the Jovian satellites.
TABLE 3
Satellite-I.A.U. Committee Names-Alternative Names Suggested Here
J V-Amalthea-Amalthea
VI-Himalia-Maia
VII-Elara-Hera
VIII-Pasiphaë-Alcmene
IX-Sinope-Leto
X-Lysithea-Demeter
XI-Carme-Semele
XII-Anake-Danaë
XIII-Leda-Leda
XIV--
But that time is not long off. There are thirty-one known moons of Jupiter, Saturn, Uranus and Neptune. None has been photographed close up. The decision has recently been made to name features on the moons in the outer solar system after mythological figures from all cultures. However, very soon the Voyager mission will obtain high-resolution images of about ten of them, in addition to the rings of Saturn. The total surface area of the small objects in the outer solar system greatly exceeds the areas of Mercury, Venus, Earth, Moon, Mars, Phobos and Deimos together. There will be ample opportunity for all human occupations and cultures to be represented eventually, and I daresay provisions for nonhuman species can also be made. There are probably more professional astronomers alive today than in the total prior recorded history of mankind. I suppose that many of us will also be commemorated in the outer solar system-a crater on Callisto, a volcano on Titan, a ridge on Miranda, a glacier on Halley’s comet. (Comets, incidentally, are given the names of their discoverers.) I sometimes wonder what the arrangement will be-whether those who are bitter rivals will be separated by being placed on different worlds, and whether those whose discoveries were collaborative will nestle together, crater rampart to crater rampart. There have been objections that political philosophers are too controversial. I myself would be delighted to see two enormous, adjacent craters called Adam Smith and Karl Marx. There are even enough objects in the solar system for dead political and military leaders to be accommodated. There are those who have advocated supporting astronomy by selling crater names to the highest bidders, but I think this goes rather too far.
THERE IS A curious problem about names in the outer solar system. Many of the objects there have extremely low density, as if they were made of ice, great fluffy snowballs tens or hundreds of miles across. While objects impacting these bodies will certainly produce craters, craters in ice will not last very long. At least for some objects in the outer solar system, named features may be transient. Perhaps that is a good thing: it would give us a chance to revise our opinions of politicians and others, and will give eventual recourse if flushes of national or ideological fervor are reflected in solar system nomenclature. The history of astronomy shows that some suggestions for celestial nomenclature are better ignored. For example, in 1688 Erhard Weigel at Jena proposed a revision of the ordinary zodiacal constellations-the lion, virgin, fish and water carrier that people have in mind when they ask you what “sign” you are. Weigel proposed instead a “heraldic sky” in which the royal families of Europe would be represented by their tutelary animals: a lion and a unicorn for England, for example. I hate to imagine descriptive stellar astronomy today had that idea been adopted in the seventeenth century. The sky would be carved into two hundred tiny patches, one for each nation-state existing at the time.
The naming of the solar system is fundamentally not a task for the exact sciences. It has historically encountered prejudice and jingoism and lack of foresight at every turn. However, while it may be a little early for self-congratulation, I think astronomers have recently taken some major steps to deprovincialize the nomenclature and make it representative of all of humanity. There are those who think it is a pointless, or at least thankless, task. But some of us are convinced it is important. Our remote descendants will be using our nomenclature for their homes: on the broiling surface of Mercury; by the banks of the Martian valleys; on the slopes of Titanian volcanoes; or on the frozen landscape of distant Pluto, where the Sun appears as a point of bright light in a sky of unremitting blackness. Their view of us, of what we cherish and hold dear, may be determined largely by how we name the moons and planets today.
[10] Kowal has also recently discovered a very interesting small object orbiting the Sun between the orbits of Uranus and Saturn. It may be the largest member of a new asteroid belt. Kowal proposes calling it Chiron, after the centaur who educated many Greek mythological gods and heroes. If other trans-Saturnian asteroids are discovered, they can be named after other centaurs.